abstract
Magnetic measurements, x-ray diffraction and Mossbauer spectroscopy were used to characterize a nanostructured fcc Fe23Cu77 at.% alloy prepared by high-energy ball-milling, addressing in particular the effect of clustering on the nature of the interacting magnetic entities. The interpretation of magnetization measurements leads to the conclusion that grains, whose mean size is similar to 16 nm, contain two populations of magnetic Fe-rich nanoclusters with a bimodal size distribution. These two sets of clusters contain about 14 and 400 Fe atoms and have magnetic moments of 30 mu(B) and 860 mu(B), respectively. The inter-cluster ferromagnetic interactions that lead to superferromagnetism with a Curie temperature T-C similar to 220 K can be described by a mean field determined by the smaller clusters only, which account for 90% of the magnetization.
keywords
FE-CU ALLOYS; FEXCU100-X SOLID-SOLUTIONS; X-RAY-SCATTERING; MAGNETIC-PROPERTIES; IMMISCIBLE ELEMENTS; SPIN-GLASS; 2-PHASE COEXISTENCE; MOSSBAUER-SPECTRA; BEHAVIOR; SYSTEMS
subject category
Physics
authors
Silva, NJO; Amaral, JS; Amaral, VS; Costa, BFO; Le Caer, G
our authors
João Cunha de Sequeira Amaral
Assistant Researcher
Nuno João Silva
Principal Researcher
Vitor Brás Sequeira Amaral
Full professoracknowledgements
N J O Silva and J S Amaral acknowledge scholarships by FCT (SFRH/BD/10383/2002 and SFRH/BD/17961/2004 respectively). This work is partially supported by project POCTI/CTM/61284/2004 from FCT and FEDER. The possibility of performing the SQUID magnetic measurements in the Materials Institute of the University of Porto (IFIMUP) is gratefully acknowledged. B F O Costa and G Le Caer gratefully acknowledge the financial support of the French Portuguese bilateral program PESSOA (grant no. 14617RE).